+/// This file contains the declaration of the Type class. For more "Type" type
+/// stuff, look in DerivedTypes.h.
+///
+/// The instances of the Type class are immutable: once they are created,
+/// they are never changed. Also note that only one instance of a particular
+/// type is ever created. Thus seeing if two types are equal is a matter of
+/// doing a trivial pointer comparison. To enforce that no two equal instances
+/// are created, Type instances can only be created via static factory methods
+/// in class Type and in derived classes.
+///
+/// Once allocated, Types are never free'd, unless they are an abstract type
+/// that is resolved to a more concrete type.
+///
+/// Types themself don't have a name, and can be named either by:
+/// - using SymbolTable instance, typically from some Module,
+/// - using convenience methods in the Module class (which uses module's
+/// SymbolTable too).
+///
+/// Opaque types are simple derived types with no state. There may be many
+/// different Opaque type objects floating around, but two are only considered
+/// identical if they are pointer equals of each other. This allows us to have
+/// two opaque types that end up resolving to different concrete types later.
+///
+/// Opaque types are also kinda weird and scary and different because they have
+/// to keep a list of uses of the type. When, through linking, parsing, or
+/// bitcode reading, they become resolved, they need to find and update all
+/// users of the unknown type, causing them to reference a new, more concrete
+/// type. Opaque types are deleted when their use list dwindles to zero users.
+///
+/// @brief Root of type hierarchy
+class Type : public AbstractTypeUser {
+public:
+ //===-------------------------------------------------------------------===//